This invention relates generally to magnetic field sensors and, more particularly, to a system and method that use an AC current carrying elastic element (e.g., wire) which vibrates or moves in the presence of a magnetic field, and using the wire movement to determine one or more characteristics of the magnetic field. The frequency of the AC current is matched to the mechanical resonant frequency of the elastic element.
Typical magnetic field sensors in use today include compass needles, Hall probes and super-conductive quantum interference devices (xe2x80x9cSQUIDsxe2x80x9d). The compass needle was discovered about 2,000 years ago by the Chinese, and the Hall probes and SQUIDs were developed fairly recently. The particular sensor one might use in a given situation often depends upon several factors such as the required accuracy, sensitivity and economic constraints. For example, a compass needle is easy to use, inexpensive and does not require electric power or circuits, but it can only indicate the direction of a field. Hall probes are more robust and can measure fields over a large range of field strengths, but their accuracy is compromised by temperature changes and they have problems related to baseline drift, noisy signals and fail in high radiation environments. The most sophisticated magnetic field sensors are the SQUIDs, which can measure magnetic fields with extremely high precision. SQUIDs require liquid helium and complex circuitry to operate, however, making them expensive and impractical.
A system for sensing fields in accordance with embodiments of the present invention includes a wire having an interior wire portion and an exterior wire portion, the wire connected at a first and a second location to a base with an interior wire portion between the connection locations having an apex spaced apart from the base. A monitoring system detects movement of the wire at least at the interior wire portion while an electrical current is sent through the wire and a magnetic field surrounds at least the interior wire portion. A reporting system determines one or more characteristics of the magnetic field based upon the detected movement of the interior wire portion.
In one embodiment, the interior wire portion may have a circular or loop configuration. Alternatively, the interior wire portion may include a square configuration. In another embodiment, the monitoring system includes a set of electrodes spaced apart to form a capacitor. The interior wire movement in between the electrodes alters a capacitance value across the electrodes. The reporting system may determine the magnetic field characteristics based upon the altered capacitance values. The monitoring system alternatively may include a photo emitter that emits light towards an inlet in a photo detector. In this example, the interior wire movement deflects at least a portion of the light away from the photo detector inlet. Here, the reporting system may determine the magnetic field characteristics based upon an amount of light deflected away from the inlet.
A method for sensing fields in accordance with embodiments of the present invention includes detecting movement in a wire while sending an electrical current through the wire and a magnetic field surrounds the wire, and determining one or more characteristics of the magnetic field based upon the detected movement of the wire.
The present invention provides a convenient, efficient and inexpensive system and method for sensing magnetic fields. Additionally, the present invention enables magnetic fields to be sensed in environments where conventional devices have difficulty or are unable to function. Further, the present invention is easily manufactured and does not require expensive materials for assembly.